FIELD OF THE INVENTION
The present invention relates to an ink jet cartridge containing liquid ink, a manufacturing method thereof, an ink jet head and printer using the cartridge, and is usable with a copying machine, a facsimile machine or another recording apparatus, communication apparatus, office equipment, combined machine or printer.
Heretofore, an ink cartridge for an ink jet recording apparatus may have been integrally formed with an ink jet head, and when the ink in the cartridge is used up, the unified head and container are disposed of. The quantity of the ink remaining in the cartridge is decided by the ink retaining capacity of a sponge (vacuum producing material) occupying the entirety of the space in the cartridge, and it is relatively large. Japanese Laid-Open Patent Application No. 87242/1988 discloses such an ink container. The ink container contains a foamed material, and it is integral with an ejection orifices. In such an ink container, in order to accommodate the ink in the porous material such as foamed polyurethane material, the production of the vacuum and the ink retention (prevention of ink leakage from the ink container) are accomplished by the capillary force of the foamed material. However, the foamed material is required to be filled in the entirety of the ink container, and therefore, the quantity of ink therein is limited, and the quantity of non-usable ink is relatively large. This means that the ink use efficiency is low. It is difficult to detect the remaining amount of the ink therein. In addition, during the ink consumption period, the negative pressure gradually changes, and therefore, it is difficult to maintain a substantially constant vacuum.
Japanese Laid-Open Patent Application No. 522/1990 discloses that the ink cartridge contains substantially only the ink. More particularly, it discloses an integral ink jet recording head and ink container, comprising a primary ink container for containing a large amount of the ink at an upper position, and a small porous material between the ink jet recording head therebelow. It is stated that ink use efficiency is improved because only the ink is disposed in the ink passage without the porous material contained in the ink container. In addition, a secondary ink container capable of containing the ink is provided at a side of the porous material, which is effective to receive ink that flows from the primary ink container due to expansion of the air in the primary ink container upon a temperature rise (pressure decrease), so as to maintain a substantially constant negative pressure of the recording head during the recording operation.
In this structure, when the recording operation is not carried out, the porous material is filled with a very large amount of the ink from the primary ink container containing a large amount of the ink above the porous material, and therefore, the porous material itself can hardly produce the negative pressure. For this reason, the ink leaks out of the orifice of the ink jet recording head through only small impacts, and therefore, the structure is not practical. If this container is used as a exchangeable ink cartridge to be mounted to an ink jet recording head, the ink can leak out of the porous material, and therefore, it is still not practical.
In an ink cartridge, the ink may be sealingly contained in a bladder, and the negative pressure of the bladder can be maintained constant using a spring structure, but this is expensive, and it is difficult to mass-produce with the correct performance of the spring structure. In the field of the ink jet printing (non-contact type printing) an inexpensive ink cartridge having proper performance has not been accomplished, and has long been desired.
The inventors have investigated from the standpoint of properly supplying the ink corresponding to the ejection of the ink from the recording head during the printing operation and also from the standpoint of preventing ink leakage through the ejection outlet when the printing operation is not carried out. As a result, it has been found that the fundamental structure comprises a chamber for containing substantially only the ink to be supplied to a second chamber containing a vacuum producing material and having an air vent, the first chamber being substantially hermetically closed with the exception of communicating with the first container.
Japanese Laid-Open Patent Application No. 16385/1982 discloses a recording pen having a recording tip which is contacted to a recording material during the recording operation. The recording tip has an ink absorbing and retaining nature, and the ink is supplied thereto. Therefore, the recording tip is exposed to ambience, as contrasted to the ink jet recording apparatus. This Japanese laid-open patent application is directed only to the overflow of the ink through the recording tip.
It comprises as essential elements a first liquid absorbing material, and a second absorbing material which absorbs less ink than the first absorbing material (although absorbing a small amount of the ink), the second absorbing material being disposed above the first absorbing material at a position closer to an air vent, a central chamber from which the recording tip is projected downwardly, and hermetically closed in accommodating chamber to supply the ink to opposite sides of the chamber. With this structure, when the air in the closed ink container expands due to the ambient temperature rise with the result of the ink in the ink container being forced into the first absorbing material, the ink incapable of being retained by the first absorbing material is absorbed by the second absorbing material, so that overflowing droplets of ink from the writing tip can be prevented. It also discloses provision of a constant width groove which is effective, when one of the two closed ink containers contains only air, to permit the expanded air to escape through the air vent. The groove is extended from the bottom end to the top end on a side surface which is different from a partition wall between the central chamber and the closed ink container. When this structure is used for an ink jet recording head, ink leakage through the air vent has been confirmed, as expected because of the fundamental difference between contact recording and non-contact recording. This problem is not recognized in the field of recording pens. In addition, the constant width groove serves to promote the discharge of ink together with air, therefore promotes ink leakage.
Additionally, the ink consumptions of the two ink containers are not the same. If one of the containers becomes empty first, the ink jet recording operation is no longer possible despite the fact that a large amount of ink is remaining in the other ink container. This is because a large amount of air is introduced into the first absorbing material with the result of incapacitating the ink supply. This is against the aim of the present invention.